In wellbore drilling, a drill bit is attached to a drill string, lowered into a well, and rotated in contact with a subterranean zone (e.g., a formation, a portion of a formation, or multiple formations). The rotation of the drill bit breaks and fractures the subterranean zone forming a wellbore. A drilling fluid (also known as drilling mud) is circulated down the drill string and through nozzles provided in the drill bit to the bottom of the wellbore, and then upward toward the surface through an annulus formed between the drill string and the wall of the wellbore. The drilling fluid serves many purposes including cooling the drill bit, supplying hydrostatic pressure upon the formation penetrated by the wellbore to prevent fluids from flowing into the wellbore, reducing torque and drag between the drill string and the wellbore, carrying the formation cuttings, i.e., the portions of the formation that are fractured by the rotating drill bit, to the surface, and other purposes.
A high pressure pump (sometimes known as a mud pump) powers the circulation of the drilling fluid through the wellbore drilling system under high pressure. In some situations, the mud pump can be a positive displacement pump (PDM) having an expanding cavity on the suction side and a decreasing cavity on the discharge side. For example, a positive displacement mud pump can include a lobe and a progressive cavity.
Like reference symbols in the various drawings indicate like elements.